There has been a longstanding need to provide a means of efficiently cooling a utility-scale heat engine without using evaporation as the cooling mechanism. Though there are many different sources of energy in the world today, the overwhelming majority all boil water to extract work from a steam turbine. Coal, oil, solar thermal, geothermal, and biomass all generate power in this way. Natural gas power plants either use the gas to boil water for a steam turbine or else simply run the gas through a gas turbine. In either case, however, the exhaust from the turbine needs to be cooled to the lowest reasonably achievable temperature so as to maximize the turbine's efficiency.
The conventional method for cooling the exhaust from a turbine is to run it through a heat exchanger with liquid water at ambient conditions. This drastically raises the temperature of the water, causing it to either boil outright or have a dramatically increased vapor pressure, increasing evaporation. In either case the cooling body of water is kept at ambient temperature by allowing evaporation. While this is an effective method for increasing turbine efficiency, it raises the significant problem of water usage.
In both traditional and renewable power plants, water usage is becoming an increasingly large barrier to permitting and construction of new power plants. This is a particularly severe problem for solar thermal power plants. Solar thermal plants require vast amounts of land and a large daily irradiance to maximize their return. They are therefore generally constructed in desert environments, where land is very inexpensive and the sun shines brightly for most of the year. These are the advantages of a desert environment, but there is an associated price. Deserts have very little water available, and what little exists is strictly monitored by local governments. Increasingly few municipalities are willing to allow power plants to consume vast amounts of water when farmers and other citizens need that water to survive. The resistance to evaporative cooling is causing many proposed power plants to switch to a dry cooling mechanism.
In general, dry cooling causes a plant to reduce its energy output by approximately 10%. This decrease in efficiency is caused by both the increase in the temperature of the cooling water from not allowing it to evaporate and by the power required to run blowers for air cooling. The current dry cooling systems use heat fins and blowers to extract the energy from the water. The blowers must run constantly to cool the water, causing efficiency losses because the water must be cooled during the day, rather than at night, when the ambient temperature is significantly lower. Thus, there is a need for a dry cooling system that ameliorates the efficiency loss from the lack of evaporative cooling.
There has also been a long-standing need to provide energy generation from renewable sources. Various renewable energy sources have been pursued, such as solar energy, wind, geothermal, and biomass for biofuels as well as others.
Solar radiation has long been a prime candidate for fulfilling this need. Various approaches have been taken to achieve energy generation from solar radiation. To that end, much focus has been directed to creating a low cost solar energy conversion system that functions with high efficiency and requires little maintenance.
For example, solar panels formed of photovoltaic cells (solar cells) are used to transform light to electricity. Such systems have been implemented in various applications. Solar panels have been generally effective for small-scale electrical generation, such as powering small electronics, electrical generation for residential applications, and electrical generation for space-based systems. However, current solar panel technology has been ineffective for large-scale uses, such as electrical generation sufficient for municipal applications. The costs associated with such large-scale usages have been prohibitive. Current solar panels are relatively expensive and do not allow cost-effective energy storage.
Other approaches include concentrating solar radiation on solar collectors for energy generation, commonly referred to as concentrated solar power (CSP). CSP systems typically use reflective surfaces to concentrate the sun's energy from a large surface area on to a solar collector. For example, the concentrated solar energy can be used to heat a working fluid. The heated fluid is then used to power a turbine to generate electricity. Alternatively, photovoltaic cells can be used at the solar collector, eliminating the need for numerous, expensive cells. In an effort to maximize efficiency, the reflective surfaces of CSP systems can be coupled to a device that tracks the sun's movement, maintaining a focus on a receiver target throughout the day. Using this approach, the CSP system can optimize the level of solar radiation directed towards the solar collector.
Although such CSP systems are better than traditional flat-panel photovoltaic cells for large-scale applications, shortfalls exist. For example, glass and metal reflector assemblies are expensive to manufacture, ship and install. Further, current tracking devices used with CSP can be relatively expensive and complicated. As a result, current approaches have yet to achieve significant market penetration because of cost issues.
Biomass production, such as algae and other microorganisms, has increasingly been of interest. The potential usage of such material is found across a wide range of applications, including biofuel feedstock production, fertilizer, nutritional supplements, pollution control, and other uses.
Current approaches for biomass production include “closed-air” systems that contain biomass production within a controlled environment, limiting exposure to outside air. Examples of such systems include closed photo-bioreactor structures forming a closed container for housing a culture medium for generating biomass. Having a controlled environment helps maximize the generation of algal material by limiting exposure to invasive species as well as controlling other environmental factors that promote algal growth. Closed-air systems significantly reduce evaporation and therefore significantly reduce demands on water resources. In addition, closed-air systems facilitate the sequestration of carbon dioxide gas, which promotes algal growth, eases compliance with environmental regulations, and, according to a large number of scientists, benefits the environment generally. However, such systems can be expensive and, in many instances, cost prohibitive.
It should be appreciated that there remains a need for a system and method of generating energy from solar radiation in a low-cost, large-scale manner. There also exists a need for a closed-air photo-bioreactor to promote algal growth in a low-cost, large-scale manner. The present disclosure fulfills these needs and others.